1. Field of the Invention
This invention relates to image sensors used in facsimile machines, copiers, optical character readers, etc.
2. Description of Related Art
FIG. 1 shows a typical conventional image sensor. FIG. 1 is a transverse sectional view of main parts of the image sensor on a plane perpendicular to the scanning direction. The image sensor is provided with a transparent cover (glass cover) 11 mounted on the top of a frame 10. Within the frame 10, a board 13 is disposed for; 13 containing a light emitting element 12. The element 12 illuminates an object, such as a manuscript (not shown), on the top surface of the glass cover 11. A rod lens array 14 serves as an optical system for converging reflected light from the manuscript. A board 16 contains a light receiving element 15 for receiving the light through the rod lens array 14.
FIG. 2 shows a transverse sectional view of main parts of another image sensor. This image sensor is basically the same as that shown in FIG. 1; a glass cover 11 is mounted on the top of a frame 10. Within the frame 10, there are disposed a board 13 containing a light emitting element 12, a rod lens array 14, and a board 16 containing a light receiving element 15.
Each image sensor as described above has a control block for controlling electric signals of the light emitting element, light receiving element, etc. This control block is usually made up of a package of electronic parts such as variable resistors and capacitors.
The image sensor shown in FIG. 1 includes an electronic parts package 20 soldered by solder 21 to the board 16. The image sensor shown in FIG. 2 includes a hybrid board 26 on which a hybrid electronic parts package 20 is mounted; the hybrid board 26 is located in the space between the bottom of the frame 10 and the board 16, and is electrically connected to a lead frame 27 soldered by solder 28 to the board 16.
However, if the electronic parts package 20 is mounted directly on the board 16 as shown in FIG. 1, solder flux is prone to be scattered on the light receiving element 15 when soldering the package to the board, and there is a chance that the image quality provided by the light receiving element 15 may be degraded.
In both image sensor examples, the electronic parts are located within the frame, thus it is difficult to adjust the electronic parts such as the variable resistors making up the control block after the completion of assembly of the image sensor; if the frame, etc., is subjected to any working process to facilitate adjustments, the production cost increases.
Further, since the electronic parts are mounted within the frame, replacement of the electronic parts is not easy; it is difficult to change the electrical characteristics of the control block for increasing variations of models.